Security systems typically collect data of the environment, analyze the data to detect a security threat, and then perform an action (e.g., generate an alarm) when a security threat is detected. For example, a home security system may include one or more cameras to collect images of different areas of a house (e.g., at the front door, at the windows, etc.). When an intruder breaks into the house, the intruder's action can be captured by the cameras. The images can then be transmitted to a processing center, where the images can be analyzed to determine that an intrusion has taken place. The images can be analyzed by human beings, by computers (e.g., by running a software program that compares the images against certain image patterns that are representative of intrusion), or by a combination of both. After determining that an intrusion has taken place, the processing center can then take certain measures, such as notifying the law enforcement, the home owner, etc., about the intrusion.
Besides image-based detection, security threats can also be detected based on acoustic signals (e.g., sound). For example, a rapid change in the intensity of acoustic signals collected from the interiors of a house may also indicate that an event that poses a security threat (e.g., a home intrusion) has occurred. For example, acoustic signals associated with various actions indicative of security threats, such as screaming, yelling, breaking of things, etc., typically include rapid change in the intensity. Therefore, a home security system may also detect security threats by detecting rapid change in the intensity of the acoustic signals collected from the interior of the house.
Compared with image-based detection, acoustics-based detection provides a number of advantages. For example, in a case where a home security system provides 24-hour non-stop monitoring, the capturing of acoustic signals can be less intrusive to occupants of the home than the capturing of images. Moreover, acoustic signals typically require less network bandwidth and computation resources for transmission and processing than image data. Therefore, acoustics-based detection has become an important component of home security systems, where network bandwidth and computation resources are typically more limited.
However, an acoustic-based detection system can still consume considerable amount of network bandwidth and computation resources, if the system transmits all of the collected sound data, continuously and indiscriminately, to the processing center.